Managing and monitoring connected devices in a network is important for network administrators in local area network applications and other much larger more complex networks. Network management systems are utilized to monitor, interpret and control the operation of a network. Typically, the network management system includes agents that reside on network devices that monitor and accumulate operational data and detect exceptional events. A manager is provided at a network management station that can request operational data and/or receive event notifications from one or more network devices via the network device agents. The manager can be equipped to interpret the operational data and/or received event notifications from the agents. Additionally, the manager can be equipped to effect control of network operations by transmitting command requests to the agents, which then execute the command requests.
Several protocols have been developed to enable management and monitoring of devices connected to a network. These protocols often include objects and procedures for accessing information associated with a network attached device. The Simple Network Management Protocol (SNMP) is an example of a relatively well known protocol for managing and monitoring network devices. The SNMP protocol uses User Datagram Protocol (UDP) packets to send and receive the information sent back and forth between management software and SNMP agents. SNMP was developed to provide a tool for multi-vendor, interoperable network management. SNMP includes a set of standards for network management including a protocol, database structure specification and a set of data objects. Network administrators can address queries and commands to network nodes and devices. SNMP monitors network performance and status, controls operational parameters and reports, analyzes and isolates faults. The protocol does these functions by transporting management information between “Managers” and “Agents”.
SNMP defines three basic components, an agent, a manager and a Management Information Base (MIB). An agent is a component that resides within a managed network device such as a host, gateway, or terminal server. Each agents stores management data and respond to management request for data. An agent can also send an unsolicited SNMP message referred to as a “TRAP” to a manager after sensing a predefined condition. A manager is a component that resides in a network management station. The manager provides an administrator with the functionality to transmit query and control commands to an agent. A MIB is a managed object database, accessible to agents and manipulated via SNMP for network management application. For example, the MIB may specify data variables which track statistics on the status of network traffic, incoming and outgoing data and failures (e.g., routing failures).
SNMP specifies five types of commands or verbs called Protocol Data Units (PDUs): GetRequest, GetNextRequest, SetRequest, GetResponse and Trap. Agents retrieve management data after receiving a GetRequest or a GetNextRequest. Manager use GetNextRequest to retrieve single values of the managed objects. The GetNextRequest is issued by the manager to begin a primitive block transfer and the agent returns the selected data with a GetResponse verb. Managers use SetRequest commands for instructing agents to alter MIB variables, while “TRAPS” are unsolicited messages sent by agents to managers after sensing predefined conditions. The second version of SNMP introduced two additional operations: Inform and GetBulk. Inform allows one manager to send trap type information to another manager and request a response. GetBulk allows a manager to retrieve efficiently large blocks of data, such as multiple rows in a table, which would otherwise require the transmission of many small blocks of data.
SNMP was originally designed for network management of single networks. However, recently the need and ability to interconnect networks has evolved. New technologies have emerged to make it possible to interconnect many disparate physical networks and make them function as a single coordinated unit. Internetworking makes is possible for a host to communicate with hosts on different networks. The size of an internet or group of interconnected networks can be quite large and complex making network management more complex. Some tools such as SNMP have not been designed to operate in such large networks. For example, devices on networks can include similar Internet Protocol (IP) addresses. When the networks are connected to one another, the IP addresses are duplicated. SNMP has no mechanism to differentiate between devices with similar IP addresses amongst different interconnected networks. Conventionally, a network administrator would have to reconfigure devices on the network to eliminate duplicate IP addresses prior to utilizing SNMP as a network management tool for large complex interconnected networks.